The present invention relates to a dryer control system for use in manufacturing gypsum board.
Gypsum board is produced by extruding a gypsum, water and foam slurry between two continuous paper sheets, cutting the resulting ribbon into boards, and passing the boards through a board dryer. In recent years, there has been a move to automate the gypsum board manufacturing process. However, attempts to integrate automatic control of both the mixer and the dryer have been limited or have experienced shortcomings. In the past, dryer control has been done by measuring moisture content of the gypsum boards as they exit the dryer and manually adjusting the dryer temperature accordingly. However, such a procedure relies on trial and error and operator skill and attentiveness, especially when changes in board formulation occur. Additionally, in currently known systems, operators have to adjust the dryer temperature manually to compensate for gaps that occur in the line of boards introduced to the dryer. Such gaps are typically caused by boards being rejected after the cutting process, and by spaces in the board line created at the start and end of a production run. Failure to adjust the dryer temperature to compensate for changes in the dryer evaporative load that result from changes in board formulations or gaps in the board line can result in over dried boards.
It is therefore desirable to provide an automated dryer control system and method in which the temperature of the board dryer is automatically adjusted to account for different board formulations, lengths and also gaps of varying sizes which occur in the line of boards provided to the dryer.
The present invention provides a dryer control system and method wherein the load of boards to be provided to the dryer is divided up into successive segments. A desired amount of water to be evaporated from each segment is determined based on the amount of water used to produce each segment. The desired amount of water to be evaporated from each segment is used as a basis for continuously calculating the evaporation load for the dryer and controlling the amount of energy provided to the dryer accordingly.
According to one aspect of the present invention, there is provided a method for controlling temperature of a dryer in a gypsum board production line in which a load that includes a line of boards is provided to the dryer, comprising the steps of dividing the load to be provided to the dryer into segments along a length of the load, determining a desired amount of water to be evaporated from each of the load segments, determining the amount of energy required to evaporate the desired amounts of water from the load segments located in the dryer at a particular time, and adjusting the heat energy provided to the dryer according to the determined amount of energy.
According to another aspect of the invention, there is provided a gypsum board drying device for a gypsum board production line, comprising a dryer having a heat energy source for providing heat energy to the dryer, a transfer system for transferring a load comprising a line of gypsum boards to and through the dryer, and a control system for the dryer. The control system for the dryer includes determining means for dividing the load to be transferred to the dryer into segments along its length and determining a desired amount of water to be evaporated from each of the load segments, calculation means responsive to the determining means for determining the amount of energy required to evaporate the desired amounts of water from all of the load segments located in the dryer during a particular time period, and adjustment means responsive to the calculation means and operatively connected to the heat energy source for adjusting the heat energy provided to the dryer according to the determined amount of energy.
According to a further aspect of the invention, there is provided a dryer control system for controlling the operation of a dryer in a gypsum board production line in which a load that includes a line of gypsum boards is provided to the dryer, the system comprising determining means for measuring the amount of water provided to a mixer station of the production line, dividing the load into a series of consecutive load segments of uniform length, and determining and storing a desired amount of water to be evaporated from each of the consecutive load segments based on the measured amount of water, calculating means responsive to the determining means for determining an evaporation load of the dryer based on the desired amounts of water to be evaporated from all of the load segments located in the dryer at a particular time, and adjustment means responsive to the calculating means for controlling a heating element of the dryer to adjust heat energy provided to the dryer according to the determined evaporation load.